Electric furnace method and apparatus.



E. WEINTRAUB.

ELECTRIC FURNAGE METHOD AND APPARATUS.

APPLICATION FILED OCT27, 1909.

Patented Mar. 5, 1912.

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WITNEEISEE" UNITED sTATEs PATENT oEEIoE.

EZECHIEL WEINTRAUB, F LYNN. MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRICCOMPANY. A CORPORATION OF NEW YORK.

ELECTRIC FURNACE METHOD AAND APPARATUS.

Specification of Letters Patent.

Patented Mar. 5, 1912.

Application filed October 27, 1909. Serial No. 524.947.

To all w/zvo'm 'it may concern;

Be it known that I. Emiel-lim. lV E1N'rR.\l'n. a citizen of the UnitedVStates. residing at Lynn. in the county of Essex. State ofMassachusetts. have invented certain new and useful lmprovements inElectric Furnace Methods and Apparatus, of which the following is aspecification.

My present invention relates to electric furnaces` and comprises afurnace operative with electrical energy of high potential. andespecially adapted for the treatment and fusion of refractory elementsand compounds.

My invention also includes the method whereby refractory materials. eventhough but slightly conductive. can be used as electrodes for a highpotential arc. and may there be treated and even fused by the heatingaction of that arc.

More specifically. my invention contemplates the purification and fusionof boron or the dissociation of boron compounds when used as anelectrode for the high potential furnace herein disclosed.

The drawing forming a part of this specitication is an elevationsomewhat diagrammatic. illustrating the general arrangement of theseveral elements and the general construction of the furnacev whenbuilt. ou a small scale.

The furnace comprises a gas-tight envelop 1 of glass. copper or othermaterial` inert with respect to the materials under treatment. andprovided with an outlet 2 by which connection may be made with a vacuumpump. and also provided with an inlet 3 by which hydrogen or othersuitable gas or gases can be introduced. Removable closures Jr and 5 areprovided for the ends of the furnace. and serve to support copper tubes(i and T. closed at their ends and carrying respectively the clamps Sand t) in which are mounted sticks or rods and l1 of the material to besubjected to heat treatment. To secure water cooling for the coppertubes and 7,1 provide each of them with longitudinal partitions 1Q, 13extending almost to the closed inner end of the tube and serving todivide the tube into two separate channels through which water may bekept flowing. Electrical connection is made between the terminals 14 and15 and a source of current of high potential as-the secondary ot' thetransformer 16 by means of conductors 1T, 18. f

vThe Vpressure of hydrogen within the chamber is regulated to accordwith the work in hand and may vary all the way from atmospheric pressuredown to as low a l'nessure as about 5 inches mercury.

Current is lsupplied to the furnace atpotential preferably in theneighborhood'of 15.00() to 30.000 volts and may be either alternatingcurrent or direct current. Direct current of a very high voltagesuitable for thisI work. can be obtained through a mercury arc rectifieroperating on an alternating current source of high voltage. The current.being at this high voltage jumps the gap between the electrodes atstarting and establishes an arc without the necessity of bringing theelectrodes into initial cont-act. This method is therefore speciallyapplicable to the treatment of material which is a poor conductor tobegin with as the high potential applied establishes au arc in spite ofthe slight conductivity of the material of the electrode.

The presence of an appreciable quantity of hydrogen or other inert gaswithin the furnace chamber restricts the length of the arc andconcentrates its thermal action on the tips of the electrodes. There istherefore little tendency for the arc to wander about over the electrodeor to jump to the holding clamps or other parts of the furnace. rlhis isespecially important on ac-` count of the tendency of the high potentialto lengthen the arc when it is once established.

Both electrodes may be of the same material or if absolute purity of theresulting product is not desired, the cooperating electrode may be ofsome. other material. Both electrodes melt at their ends and byprolonging the run both can be melted down into dense homogeneousglobules. lt will be understood that fusion is not carried far enough tocontaminate the globules by metal fused from the supporting clamps.though if the electrode consists 'of boron held in av copper clamp thereis little danger of contaminating the boron with copper as these twoelements do notalloy with one another.`

It. will be understood that this furnace can be used in the treatmentand fusion of many refractory elements and compounds,

The tech'nicahliterature'describes the--re-' lasagna. :dierasy'spefcii-gadvanage for thev l productionof pure and conductive boronashereinafter described'moreoat length.'

Iduction of boron fanhydrid With magnesium.' lIf the theoretical amount'of magne- "s'ium sufficient to combine lvvith the oxygen v present` inthe anhydridor an excess: of magcontainsthree to four. per cent. ofmagnel V 'fanhy'dr'id,and one partmagnesium inthe endeavor to obtain theproductfree from inagnesium.-y Thev resulting product, however,

sium. f'In order to free" it from this magnesium, Moissanf-recommends. afusion 4with ,50 i

ltimes its :Weightjfeboric anhydrid. After treating theproductr in thislmanner, he reports analyses runningas-high as`98 to 99% boron. I haverepeated the experiment many times and find that the product alwayscontains appreciable oxygen, though in .other respects corresponding,Withv Moissans description. r f

It may be mentioned here that the presence of combined oxygen `is alwaysdiflicult to detect and similar cases yof mistaking a t suboxid forfanelement have occurred before.' Molssans boron 1s described by hlm asbeing a brownish-powder, lsubstantially nonconductive for'electricalcurrent, and vaporizing 'Without fusiorn I I have discovered that if thereaction ben tweenthe .boric 'anhydrid-4 and the magnesium is carried'onwith an excess of boric anhydrid, and ata higher temperature thanemployed by Moissan, boron'suboxid is produced directly freefrommagnesium.

Finely divided magnesium is thoroughly vmixedfwith iinely'ipowderedboric anhydrid,

B2Q3, in the proportions of three to Iive parts of anhydrid to one ofmagnesium. Themixture is placedin a suitable crucible, such as a clay.or graphite crucible, and-heated in a lsuitableV furnace ,to a'temperature of at least Asistance furnace." However, as the reaction* Y1300o C. to' 1000o C.; vA,,temperat-111-@,even

higher 'than this is of'.advantage.A.fThis high temperaturercau be mostconveniently 'obtained 1n an electric furnace, such as a re itself isexothermican'd `generates considerable heat, I find the required hightempera'- p ftur'e'can be .obtained`eyen in a gas-'furnace t 'if a largemass of material visusked, so that l.thel heat generatedl by thereaction is conl Qserved ,The result of the reaction whenl .f i

-ca'rried'out lunderthese conditions isboron .l m'oved, by Washing `withWater'and acidfas `current. ,i sticks progressively heat up and fuse,the bO-` l making pure fused conductive boron by suit` able. heat,treatment of vdissociable boron compounds, such as boron-suboxid, ormagne` siuniborid. The operation includes heating July-11, 1911, filedby mefDecember I havedescribed and claimed the vmethod/of -sium, and tovproduce such other changes as are necessary to make it slightlyconductive, After that, the material, preferably in the contaminatingthe boron with carbon or other foreign element.

Starting with suboxid of boron or with magnesium borid I press thematerial into sticks or rods. These sticks or rods are preheated toabout 1000o C. to render them slightly conductive and are then mountedas electrodes in the furnace shownin the accompanying drawing. As shown,they are held by the copper clamps 8, 9 which are held together bythecopper rings 19, 20. Both electrodes may be 0f the same material, orone electrode may be of some other highly refractory element, insertwith respect to boron. If the electrodes are initially separated by adistance of about one-,fourth of an inch, 'and are surrounded byhydrogen at a pressure equal to or exceeding that of five inches ofmercury, the voltage necessary to cause the current to jump the gapandstart an arc, Will be in the neighborhoodl of from 15,000 to 30,000volts. tions, the impureboron electrodes need be' but slightlyconductive. The hydrogen atmosphere keeps the arc concentrated `on theextreme ends of the boron sticks;

With such a high voltage between the electrodes, a large expenditure ofenergy is possible Without the usev of more than a small 'amount of Ifind that as the impure I boronron loses its .magnesium or oxygen, asthe lform of a stick, is mounted as anode for a furnace operation andwithout danger of l Under these condic'ase may berand becomes lvery pureand` dense. a

rThe furnace operation. above described "can be `used inl yotherrelations, as, for instance, in the fusion "of sticks pressed up 'Y.from pure boron. In this case, the fusing serves not to purify theboron, but mainly., to change it into `a denser` form. v vThe highpotential furnace herein dde v'scribed affords a means formaking boronalloys containing even-but a trace of' some other element. *'Ipovaccomplish result, 1

pure powdered boron is mixed with the other element and then pressedinto sticks and fused down, as in the case of pure boron. Thus, boronpowder and graphitized lamp black may be mixed together and finallyheated to produce dense bodies of boron chemically united with carbon.

In a modified form of furnace one electrode is a watercooled copperCrucible, the other a watercooled copper tube. The material is placed inthe crucible and the high -potential arc is made to play on the materialfrom the copper tube electrode until it is fused.

What I claim as new and desire to secure by Letters Iatentof the UnitedStates, is.l

l. An electric furnace comprising a glass envelop, means for exhaustingthe envelop, means for supplying hydrogen thereto, water-cooledstationary terminals for said furnace, means for supporting at the endof at least one terminal refractory material to constitute an electrodefor the furnace, and means for establishing and maintaining a highvoltage arc between said refractory material and the other electrode.

2. The method of fusing a refractory powder of low conductivity, whichconsists in compressing it into a stick, mounting it in a chambercontaining hydrogen and maintaining a high voltage arc to the stickuntil fused.

3. The method of forming dense, fused bodies from refractory material oflow conductivity, which consists in mounting the material as electrodefor a furnace, and there heating it progressively by a high potentialarc operating' in an inert gas.

4. The method of making pure conductiife boron, which consists inshaping impure boron into a stick and then heating said stick by runningit as electrode for a high potential are.

5. The method of making pure boron from magnesium borid2 whichconsistsin heating magnesium borid wit-h a highI potential arc running to saidborid in an inert environment.

6. The method which consists in reducing borc anhydrid with an excess ofmagnesium, shaping the resultant product into a stick, mount-ing thestick as anode for a furnace, and initiating and maintaining a highvoltage arc to said stick until the magnesium has been driven out.

7 The method of making pure boron from impure boron, which consists inshaping the impure boron into sticks, mounting them as electrodes for afurnace, initiating a high voltage are between said electrodes andconcentrating the heating action of said arc on adjacent ends of the twoopposing electrodes.

8. The method of consolidating powdered material into a dense, uniform,homogeneous body, which consists in compressing the powder into alstick, mounting the stick as electrode for a furnace, maintaining a highvoltage arc to said stick, and localizing the heating act-ion of saidarc on an end of the stick.

9. The method of making elemental boron from a dissociable boroncompound which consists in heating said compound with a high potentialarc running therefrom as an electrode in a gas inert with respect toboron.

In witness whereof I have hereunto set my hand this 26th day of October,1909.

EZECHIEL WEINTRAUB.

Witnesses:

JOHN A. MoMANUs, Jr., CHARLES A. BARNARD.

